Pivoted bar bending apparatus having means for relieving excess clamping pressure atregion of bend



1958 c. H. WARREN ETAL 2,818,903

PIVOTED BAR BENDING APPARATUS HAVING MEANS FOR RELIEVING EXCESS CLAMPING PRESSURE AT REGION OF BEND Filed June 2, 1953 2 SheetsSheet 1 lNVEA/TOR y Claude Ii Warren Gem/a .Po/lard Jan. 1958 c. H. WARREN ET AL 2,

PIVOTED BAR BENDING APPARATUS HAVING MEANS FOR RELIEVING EXCESS CLAMPING PRESSURE AT REGION OF BEND Filed June 2, 1953 v 2 Sheets-Sheet 2 Fig.4

INVEN TOR. Claudia H Warren Garb/d M. Pol/0rd 2 4 A T TOR/{E Y IVOTED BAR BENDING APPARATUS HAVING MEANS FOR RELIEVING EXCESS CLAMPING PRESSURE AT REGION OF BEND Claude H. Warren and Gerald M. Pollard, Vallejo, Calif.

Application JuneiZ, 1953, Serial. No. 359,238

3 Claims. (Cl. 153-40) (Granted'underTitle 35, U. S. Code (1952.), sec. 266) This invention .may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to apparatus and methods .for bending metal shapes and, more in particular, to method andapparatus for bending flat bar edgewise.

As is well :known, numerous different machines have been developed for'bending and working the various forms of metal blanks, and among such machines areincluded the well-known "sheet metal :bending brakes, the plate bending rolls, pipe-and :rod benders and rnanyother types. However, in most of itheseimachines, the metal is bent transversely of :its longitudinal axis and the bend produced ;is across the *relatively narrow thickness -:of the metal. OntheotherJhand, there are some 'types of work in which vit is desirable to bend the metal edgewise or, in other words, to :bend it along'its'relatively large width. Of course,.if themetal to be bent "is sufficiently narrow :or

pliable, no difiiculty will be experienced, but where the work piece is relatively wide andthick, any such attempt usually has resulted in z-fracturin'g r tearing along the outside radius of thei-bend.

One particular operation in "which :it would be most profitable to accomplish this edgewise Fbending .is the shaping of copper bus bars, such as are used in extremely long sections as electrical :conta'ct'wipers in buildings, or,

in long electrolytic'processing tanks and the like. Very frequently, it is necessary to form a shallow dip or rise in the lengths of these bus bars and, ofcourse, they require any nurribcr-ofrightaangle bends at structural corners. rHowevenzattemptsitorproduce'these bends have met with such-consistent failure ithat the prevailing and, as far vas 'is :known, ithe only practice :is to braze, silver solder,

or bolt separate :sections together to form the desired shape. fiAs will be readily apparent, any such mechani- -cal coupling of the :separate lengths constitutes a :rela- :tively tedious :operation and represents a considerable :un-

necessary waste of time .and labor. Further and even more :important :than such economic considerations is the fact'that :the electricalcharacteristics of bus bars cou- 'pled .together in such mechanical manners have been :foundtobe depreciated :and, most probably, this is .due to the necessity-of applyinglheatrfor the rbrazing or soldering. At least, it-is a certainty that-local applications of heat,such as areused'infsilversoldering, create localized strains or weak;points :in :11118311161131 which, subsequently, produce fractures when subjected :tovibrations or other physical disturbance.

In view of these "disadvantages, some attempts have been made at bending bus bars, but, as'previously indi- "nited States atent O ad :of bending 'these bars. :In the first place, it ,is common bending practice "to clamp the object to be bent against a stationary support and then toswingor move the bending beam about the bending fulcrum -or shaft. Although such amanner-of bending-maybe suitable for producing transverse bends across relatively thin work pieces, it is not satisfactory when wide bars and the like are to be shaped. Apparently, ':the adifliculty lies in the fact that such :a bending requires an excessive stretching of the metal :about the bending :shaft and, when the bar is a \Vld610fl$,lh6l6 is not .ar'sufiicient flow of metal from the inner :to the outer radius to avoid tears or fractures being produced in this "outer radius. Whatever the physical reason may be, it is clear that attempts to bend bars that are clamped to stationary plates :have not proven successful. Another :diiliculty inherent in :the bending of any flat stock lies :in the fact that :the ,full width of the stock mustbe clamped 10 :a support so as .toxmaintain the width and prevent :the anetal from crimping or folding againstr'theshaftiaroundavhich the bending .is taking place. Such a clamping, however, produces its own difficulties in that, during the bending, portions "of the metal adjacent :to the :shait thicken or upset to-such an extent that the inner radius of the :bar becomes tightly bound between the "clamp, the bansupportand the shaft. When the bar becomes bound ill'sSllGh a :manner, a'shearing 'e'ffeet is produced longitudinally of the bar due 'to the fact that the outer portions of the bar *are relatively free to move and the obvious aesultis :that the bar gives, or, in otherwordsfiractures atits weakest point, which obvious.- ly is its outer .radius because that portion reduces in thickness as the bar'is'beingibent.

It is, therefore, :an :objectcdf the present invention to provide apparatus :and method iorcold-bending'bar stock in an edgewisedirect ion.

More specific-.objectsare to provideapparatus for bending .bar edgewise in which :the 'bar :is iclamped ;to :its support :in a manner capable of minimizing stretching of the metal during the bending and, further, to provide a means for relieving the-clamping pressure during the bending a sufficient amount :to avoid binding of the bar beneaththe clamp.

Other objects are to provide an unusually simple and expeditious manner and means for z-bending :bar 'edgew'ise without producing :excessive internal "strains or fractures in the barzstock.

According to the present invention, the bending apparatus includes a :table on which the bar stock is clamped and supported during the bending, and projecting outwardly of this table, is 'a shaft around which the bar is "bent. One of the .features of the invention is that the table is rotatably driven ato carry .the bar about the shaftso that there :is arm'inimum stretching of the metal stock during the bending and, =of course, the clamp whichzsecures the bar .-fl'at sagainst the .table also rotates with 'the table. In the preferred dorms, means, such as :a heavy roller, is disposed :in alaterally spaced :position from the shaftfor engaging-the -outer:edge=o'f=therbar and pressingit against *the shaft during the :bending, this :means also being-mounted for rotation with tthe :table. The :rear :or trailing :portion of the bar is braced .or supported against any lat eral swinging movement :so as to provide the equal and opposite force zuecessa'nytto produce the bend.

in operation, after he hat iis tightly clamped in .position on the table and the outer edge forming roll is brought to bear against it, the table is .rotatably driven to carry the :bar tarcu'ately, :about the shaft. As would be -expected, .as :the :inner radius of the bar :is :pressed against the shaft, it automatically thickens or upsets, and, inview of this, .anotherieature of this invention lies in the manner zin which binding .due to such thickening is prevented. Briefly, this (feature involves the provision of means for relieving the clamping pressure in direct proportion to the degree of the bend that is being made, such relief being effected by permitting the clamp to rise a sufiicient amount to compensate for the thickening. Although a skilled operator might be able to manually release the clamp the desired amount, the invention con templates automatic means for accomplishing this result, and the automatic means is controlled by the table rotation so as to insure a direct relationship between the degree of rotation and the amount of clamping pressure release. In the preferred form, the clamp is rotatably mounted on the bending shaft and its clamping pressure is provided by a special nut that threadedly engages the shaft. Rotation of this nut in one direction produces the desired clamping effect, whilerotation in the opposite direction provides the clamping release. This rotation in the opposite direction is achieved through the use of a lever which engages the nut at one end and engages the rotating table at the other, the result being that, as the table rotates, the nut is turned and the pressure relieved. Most suitably, the pitch of the nuts threads is so designed that a certain rise or release of the clamp is effected when the nut is rotated through a 90 degree arc.

Other features of the present invention are more concerned with the structural and mechanical aspects of the apparatus and, since an understanding of them requires a rather detailed description, they are not considered appropriate for present generalized analysis.

The preferred embodiment of the invention is illustrated in the accompanying drawings of which Figs. 1 and 2 are plan and side views, respectively, while Figs. 3, 4 and 5 are vertical sections taken along lines IIIIII, IVIV and VV of Fig. 1, and Fig. 6 a plan view similar to Fig. 1 showing the position of the bending parts at the completion of bending operation.

Referring to the drawings, the functional elements of the machine all are mounted in a single cast steel frame 1 which, as may be noted, is bolted to and supported by a fabricated steel platform foundation 2, such an arrangement combining all of the machine components into a single unit that can be moved about in the shop as desired. Casting 1, as shown in the sectional drawings, is hollow and, further, it is formed with a portion of its top wall cutaway in a particular manner to form a well, or recess 3 in which is mounted a table 4. In a manner which will be described, this table is adapted to be rotated about its central vertical axis, and, to permit this rotation, the inner edge of well 3 is specially shaped.

Preferably, hydraulic means are provided for rotating the table because such means assure a steady, constantlyapplied and controlled pressure and, as may be noted in Fig. 4, these hydraulic means include a pair of oppositely-drivenpistions 6 and 7 mounted as shown in cylinders 8 and 9 which, most suitably, are bolted to I frame 1. Each of these pistons is provided, in the conventional manner, with compression retaining rings 11 as well as suitable leather piston seals 13, and the hy draulic fluid to drive the pistons is admitted into their cylinders through conduits 16 and 17. Most suitably, power for the pistons is provided by a self-contained hydraulic pump unit which includes a constant displacement pump 18 which draws its supply from anoil reservoir 19. Power for the pump may be supplied by a 5 H. P. 220/440 volt 3 phase alternating current motor 21, although power of such a magnitude probably is beyond normal demands, and, if desired, suitable control mechanism, including solenoid valves, limit switches, etc. may be provided to facilitate operations.

The need for the two pistons 6 and 7 is, as might be anticipated, to produce a reversing rotary motion in table 4 and, for this purpose, both of these pistons are connected to the table through a connecting rod 22 (Fig. l), and actually both pistons are formed as" integral extensions of a central shaft 23 which, in turn, is coupled to the connecting rod. Most suitably, shaft 23 is coupled to the connecting rod by means of a connecting rod pin 24 which is deeply anchored in a recess formed in the shaft and which projects outwardly of the shaft through a relatively heavy ring member 26 mounted on the shaft. The opposite end of connecting rod 22 is secured to table 4 by another connecting rod or pin 28 which projects upwardly from the rod into a close fit with a deep bore extending upwardly from the base of table 4.

As a result, when hydraulic power is applied to lefthand piston 6, table 4 is rotated in a clockwise direction (Fig. 1) and when the power is applied to the other piston the table moves back to its original position in the opposite direction. During this movement, it will be noted that a substantial portion of the periphery of table 4 bears against the casing wall so as to provide additional support for the table and render the machine more rigid and strong. In addition, as would be expected, the compound leverage provided by connecting rod 22 is capable of developing more than sufficient power for most any desired bending operation.

The remaining elements of the apparatus deal more directly with the actual gripping and bending of the bar to be shaped and, generally, these include (Fig. 5) a stationary shaft 31 around which the bar is bent, clamping mechanism 32 for clamping the bar to table 4 and bar-holding mechanism 33 adapted to engage the outside of the bar and press it against bending shaft 31.

As to the more specific details of these elements, shaft 31 is formed at its lower end with a laterally projecting flange 34 by means of which it is bolted to a downwardly projecting lip portion of frame 1, the shaft also having a central portion 36 of relatively large diameter and an upper portion of reduced diameter. This upper portion, as may be noted, is formed with smooth-walled lower barengaging extent 37, while the upper extent of this portion is formed with specially shaped threads 38 the functioning of which will be described later. Central portion 36 extends upwardly through frame 1 and also through table 4, the table being rotatably mounted on the shaft in any suitable manner, such as by means of a frictionless bearing ring, and the shaft as a whole is secured in position by a retaining ring 41 which may be fastened directly to the shaft'by elements such as cap screws 42. The important thing to note about this structure is that the shaft itself is stationary, while table 4, as well as other elements mounted on it, are rotatable about it.

As to these other rotatable elements, their function is to cooperatively provide what has been referred to previously as bar clamping mechanism 32 and, as may be seen, they include a clamping plate 43 which fits rotatably about portion 37 of the shaftiand a special nut 44 adapted to mesh with threads 38. When a section of bar stock is to be bent, it first is placed on table 4 beneath clamping plate 43, after which nut 44 is tightened against the plate to effect the clamping pressure.

As will be appreciated, as the bar is being bent, some force must be exerted laterally against its outer edge to hold it tightly up against the portion of the shaft around which it is to be bent and, in the illustrated form, this force is provided by bar-holding mechanism 33. The functional part of this mechanism is provided by a hardened roller 46 (Fig. 5) which is rotatably mounted on a central shaft 47, this roller being held in position by a retaining ring 48 which may be secured to the shaft by a set screw 49. Also, as will be apparent, the position of roll 46 should be adjustable in accordance with the width of the bar that is being bent, and such adjustability is provided by an elongate feed screw 51 threadedly meshed with the lower portion of shaft 47.

The inner end of feed screw 51 is reduced in size and engaged in a circular recess 52 formed in table 4, while the outer end of the feed screw is provided with means by which the screw can be rotated to move shaft 47 and its associated. elements toward and away from bending shaft 31. .In addition, it can .be sappreciated thatconsicleralileitereeawilltbeexerted as tliendnrgtrdll hut ing ails-endi g eparation, and one of-the "advantages air ithe present arrangemenfiis thatuiis fierce 'e'a be effectively "absorbedb the "shaft *47, its rear [mg ting 48 mrd' feeH screw, as 'well as by'aifeed'screw re ining-"frin'g5'53. Ring "53 engages a lateralfla'nge "54 *formd onthe feedscr'e'w and the assemblage. is secured .in,position by-a suitable lock'n'ut 56" threadedly' engaged wi'thfing53iin the manner illustrated inFig. 5.

'LDui'ingJ'a "bendin'gbperation, it *is "desirable to provide additional elements to engagefthe 'barand'i'h'old "-it"in"a proper relationship with .respeet' to ath'e -sha ft around which itfis' bingbent. one 6f*'tlfese' lemeiits is *an additional clamping ','plate 557 -=eaia a's may "be 'noted in "Figs. 1"and3, ismounted en ta'BIe t-so-asIm Frotate' w'ith the table. blampingplate :57 vis"=.-keye"dfto table 53 so "as to be movable "to'va rious appropriate "positions withre- "spect'to theplatform, and,"after?the; at .has Zbeen a'd- ,justed itmay be 'clampedhothetable y'i'b'olts 59. an addition, "the clamping 51ate mounts ":a i'sep'arate ig ri'pping plate 161 to actually -.engage the fbar, :a'n'd :this plate is movable toward "and away from such engagement by screws'62. The obviouspurposetdfitliis additionaflamping mechanism f is to securely =engflg'efthe bar atia spaced distance 'in advance of clamping mechanism '321arid=to thereby assist m echar'1ism in l'hdlding ff'ihe ib'ar fia'tly against th'e'table surface.

The other additionalwbareengaging element/is used to abut the trailing end of theibar andprevent this trailing end from swinging arcuately fa's' 'the clamped portion of "the bar is ubeingarotatably xcarrie'cllantl tbent around (bending shaft 81. Such.an .element is-iprovided bylblock 64 Z,(:Fig. 21 which .may .be .bolted .i

Stothe .upper surface offrame'd I lIf idesiredptliis.blockcan be.adjustably. mounted andfialso rean be .provided .withaxemovable Tandtreplaceable'bwearaing surface, i such -mechanicaLrefinenterits bein'g comtnon knowledge and needinglno deseription.

As has been noted, "the present' inven'tion provides several advantageousfeatures, suh' for instance as th'e fact that the bending is accomplished by clamping the bar to be bent to' a rotatable table and then rotating the table to carry the bar about the bending shaft. This particular feature is advantageous because it minimizes the metal stretching which otherwise would occur if the metal were clamped to a stationary table and then forced, by means of an arcuately-swinging beam or the like, about a bending shaft. As will be obvious, when relatively wide and thin bars are being bent any such minimizing of stretching is extremely important to avoid excess attenuation and weakening of the portions subject to the most stretch.

However, another equally important feature which also minimizes stretching and reduces fracturing is the fact that the present clamping mechanism 32 is so arranged as to permit a release of the clamping pressure as the bending progresses. This release, of course, must be accomplished by unscrewing special nut 44 but, in the present invention, the unscrewing of this nut is performed automatically and at such a controlled rate that the pressure release is directly proportional to the degree of rotation of the table. Such an automatic release is provided by coupling shaft 47 of bar holder mechanism 33 to nut 44 by means of a slotted lever 63. With these two elements so coupled, it will be appreciated that any arcuate swing of lever 63, caused by the rotation of the table and its shaft 47, will be translated into a rotational movement of nut 44. Obviously, the arrangement is such that a swing of the table in a clockwise or bending direction unscrews nut 44 to permit clamping plate 32 to rise and relieve its clamping pressure. The purpose in relieving the pressure is to avoid a binding of the bar between the clamping plate, the bending shaft and the table, such a binding being due to estationary apos'ition the manner ashown.

-a thickening or upsetting along the inner radius of the 551 afitifibingbent. Accordinguo present thinking, whenrsuch mdin'g occurs,';portions o'fthe bar along the --i'nner *radius are held tightly against the stationary shaft, "while thepo'rtions exterior to this inner radius are relaiivlyi'fre'eto travlwiththetzible and the clamp. As a 'XSlllLfi "very-substantial pull'is exerted along the inner ra'lius"andthis pull may bevisualized' as a' shearing action capable -"ofact1ng longitudinally of the "bar to eventually "causeafracturingof the metal at its'weakest joints which will 'be along itsouter attenuatedradius.

"In'the;present'*apparatus, any such'binding is avoided by a "controlled release of "the clamping pressure, and very close control of this release may be accomplished by forming threads 38 with such a specialpitchth'at rotationof 'the'table through any particular are will result in 'adesiredunscrewing'actionof nut'44. According to "'t'lre' present"practices,threads 38 are formed with a "50 'angle andnpitchof Z304". Translating this pitch into ;rdtary. motion,'itcan be'seen that the nut and clamping Ypl'ate rise approximately .O76in'ch during a degree :ar'cuate "swing of the table and -its associated elements.

f'Qther features at the invention which also are of importance include the hydraulic compound drive by :means of which the rotational travel'of the table can be closely"controlledythe adjustable mounting and support of bar hdlding roller "46 and, from an overall viewpoint, t'h'e general arrangement of the structure which providessturdiness,compactness, portability and economic operation.

,Brie'fiy reviewing the operation of the machine, a b'ar"to"bebe1it"is"placed "on table 4by sliding the bar lntopposition beneath'hold-down plate 43 and feed screw "then. rotated to move'roll'er .46 "into contact with the "exterioredge'ofthefbar. Depending .upon the thickness '(ifthebar, it "may be 'necessaryto back off nut 44 and -'manually lift lever 63 so as 'to;permit the bar to be slipped inbe'nea'th -hold-"down {plate 43. At this point -'the bar'-is-tightly held between roller46 and shaft 31, so that mit 14 and screws '62 may "be screwed down to clamp the bar tightly against the table. Also, it should be made certain that the trailing edge of the bar abuts block 64 so that, as the bar is being bent, the block will apply such equal and opposite force as is neccessary to produce the bend. With the bar so engaged the hydraulic control mechanism is actuated to drive piston 6 and rotate the table in a bar-bending, clockwise direction. After the bend is completed, the bar may be taken out by using wrench lever 63 to remove nut 44 and permit the removal of hold-down plate 43. Screw 62 also should be released to loosen gripping plate 61, whereupon the bent'bar can be slid out. If the bend is not too sharp, it will not be necessary to remove nut 44 and the bar can be slipped out simply by backing off of this nut and loosening gripping plate 61. The hydraulic control mechanism may be reversed to drive piston 7 and cause the table to return to its initial position. Such a bending operation is, as has been stated, a continuous one and one in which the necessary bends are produced without fracturing, as well as without any application of deleterious heat.

However, to avoid any misconception, it should be noted that, although the above description has been slanted toward a machine that is adapted for bending copper bus bars, it is contemplated that the machine also could be used for bending other metal stock, and, in fact, the machine described above has sufiicient power to bend even wider and thicker stock than the 4" x copper bus bars usually encountered.

Obviously, many modifications, both in structure and use may occur to those skilled in metal working and, to the extent that such modifications include the broader concepts of the invention, they are within its contemplated scope. For example, it would not be necessary to couple lever 63 to shaft 47 in the manner illustrated.

Instead, the table could be formed with a'separate projection onto which the lever could be coupled, or, perhaps, there are other equivalent mechanisms which could be substituted in entirety for the lever itself. such a lever is not absolutely necessary for proper operation of the apparatus and, if the operator is sufiiciently skilled, he can release the pressure of nut 44 manually by use of a wrench or the like. In other words, the invention is more concerned with economically producing.

smooth, unfractured bends by eliminating metal stretching and binding to as great a degree as possible, than it is with the mechanicaldetails of the mechanisms that facilitate the movements required.

We claim:

1. Bar-bending apparatus comprising a table, means for rotating the table, a bar-bending shaft projecting outwardly of the table, adjustable means rotatable with the table for pressing a table-supported bar against said shaft, a clamp rotatably mounted on the shaft for pressing said bar against the table, means threadedly mounted on the shaft for pressuring said clamp, fixed bracing means abutting the trailing portion of said bar and holding said bar against lateral movement for producing a bend in the bar as the rotated table carries it about said shaft, and lever means coupling together said table and said clamp pressuring means, rotation of said lever means with said table rotating said threaded pressuring means sufiiciently during the bending operation to relieve excess clamping pressure caused by bar upsetting.

2. Bar bending apparatus comprising a table,.hydraulic In fact,

coupling together said table and said clamp pressuring means,erotation ofsaid lever meanswith 'saidttable roftating said threaded pressuring means during the bending period to relieve excess. clamping pressure, said pressure relief being controlled by the relationship between the degree of rotation and the pitch of said threaded pressure means.

3. Bar-bending apparatus comprising a table, means for rotating the table, a' stationary bar-bending shaft projecting outwardly of the table, adjustable means rotatable with the table for pressing a table-supported bar against said shaft, a clamp rotatably mounted on the shaft for pressing said bar against the table, clamp-pressuring means mounted on and rotatable about the axis of said shaft, said pressuring means having an inclined-plane surface functioning upon rotation of said clamp-pressuring means to forcibly move the pressuring means axially along said stationary shaft whereby to varyrthe pressure exerted by said means on said clamp, fixed bracing means abutting the trailing portion of said bar and holding said bar against lateral movement for producing a bend in the bar as the rotating table carries it about said shaft, and lever means coupling together said table and said clamp-pressuring means, rotation of said lever means with said table rotating said clamp-pressuring means sufficiently during the bending operation to relieve excess clamping pressure caused by bar upsetting.

References Cited in the file of this patent UNITED STATES PATENTS 390,357 Gathman Oct. 2, 1888 699,858 Vollmer May 13, 1902 718,409 Wilson Jan. 13, 1903 734,316 r Geisenhoner July 21, 1903 1,656,003 Johnston Ian. 10, 1928 1,920,155 Fisher July 25, 1933 1,933,320 Eaton Oct. 31, 1933 FOREIGN PATENTS 26,245 Great Britain Nov. 13, 1913 

